Ear-insert microphone



June 28, 1966 A. D. BREDON 3,2

EAR-INSERT MICROPHONE Filed 001;. 16, 1962 4 Sheets-Sheet 1 ALAN D. BREDON INVENTOR Attorney June 28, 1966 A. D. BREDON 3,258,533

EAR-INSERT MICROPHONE Filed Oct. 16, 1962 4 Sheets-Sheet 2 n! 1 I TRANSMITTER $6 nil j- 9| lj) AMPLIFIER RA S'M TER 90 SHIFTER T N RECEIVER 90 [Z SHIFTER ALAN D. BRE DON INVENTOR.

BY 659w Attorney June 28, 1966 A. D. BREDON EAR-INSERT MICROPHONE 4 SheetsSheet 5 Filed Oct. 16, 1962 ALAN D. BREDON INVENTOR.

BY F;

Attorney 4 Sheets-Sheet 4 RECEIVING con.

NETWORK IMPEDANCE BALANCING A. D. BREDON EAR-INSERT MICROPHONE TR AN 8 M ITTER ALAN D. BREDON INVENTOR.

BY K 2 &

Attorney I I l I I I I I I I 76 ig I0 June 28, 1966 Filed Oct. 16, 1962 United States Patent 3,258,533 EAR-INSERT MICROPHONE Alan D. Bredon, Granada Hills, Califi, assignor to Spacelabs, Inc., Van Nuys, Calif, a corporation of California Filed Oct. 16, 1962, Ser. No. 230,906 11 Claims. (Cl. 179-1) This invention relates to transducer means for transforming human speech into electrical signals and more particularly to novel and improved microphone apparatus adapted to be worn in the ear.

There are two general paths for the transmission of sound from the mouth to the ear. One path is through the air surrounding the head. The other path is directly through the head, by air transmission through the various tubes and cavities of the head and ear, or by bone conduction, or by a combination of both.

In high noise levels prior voice-communication systems become inadequate because the systems signal-to-noise ratio becomes excessive. For such a condition a microphone capable of picking up sounds transmitted directly through the head has an advantage over conventional microphones because of the shielding effect that can be obtained, especially when used with a protective cover which will isolate the microphone from ambient sounds.

Attempts have been made heretofore to pick up speech sounds transmitted through the head by means of a microphone inserted into the outer ear. Prior to the present invention, this technique has not been considered as a satisfactory substitute for a microphone placed in proximity to the lips because of the very low signal level available at the ear and also because of the relatively steep frequency roll-off of the high end of the speech spectrum as transmitted through the head. By means of the present invention there is provided a novel and improved earinsert microphone which overcomes these limitations of the prior art and, as embodied in certain modifications, provides many other features and advantages not heretofore available.

An obvious benefit of the ear-insert microphone of the present invention is that it is effectively responsive only to the voice of the wearer and therefore discriminates against ambient sounds. Prior attempts to provide a similar function have been based on the use of throat microphones. These attempts have not been altogether satisfactory because of the almost complete absence of important speech sounds produced by the tongue, lips, and teeth. As a result, the intelligibility of speech picked up by means of throat microphones has been so poor that this technique has now been abandoned, for all practical purposes.

The ear-insert microphone of the present invention is ideally suited for use in noisy environments and is particularly useful in aerospace voice-communication systems. For example, the ear-insert microphone may be used within a pressurized helmet and/ or with circumaural protection devices or so called ear defenders, since it will not interfere with the functioning of a helmet which, with conventional microphones, will produce disagreeable speech sounds, e.g. popping due to unvoiced plosives and sibilant hisses. The ear-insert microphone of the present invention is also applicable to respiratory protective devices since it will not interfere with the mouth or with breathing.

According to the present invention there is provided novel and improved apparatus whereby the signal level output from a microphone located in the outer ear is comparable to the output level of conventional microphones of the type designed for use in proximity to the lips. Furthermore, the present invention provides novel and improved apparatus for correcting the frequency-versus- 3,258,533 Patented June 28, 1966 amplitude characteristic of the speech spectrum extant in the outer ear, and thus provide a natural-sounding speech signal of high intelligibility.

An ear-insert microphone is also of an advantage in those instances in which the microphone should be out of the way or concealed, as in the case of picking up speech from actors on a stage or set.

It is therefore the principal object of the invention to provide novel and improved means for speech communication.

Another object of the invention is to provide a novel and improved ear-insert microphone.

Yet another object of the invention is to provide a microphone which is responsive to speech but is relatively unresponsive to ambient sounds.

Still another object of the invention is to provide a novel and improved microphone which is worn in the outer ear and which is unencumbered by interconnecting wires or cords.

It is another object of the present invention to provide voice communication apparatus which is unencumbering and which will not interfere with respiratory functions or apparatus related thereto such as respirators, pressurized helmets, or the like.

A general object of this invention is to provide new and improved voice communication apparatus which overcomes disadvantages of previous means and methods heretofore intended to accomplish generally similar purposes.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which preferred structural embodiments, incorporating the principles of the present invention are shown by way of illustrative examples.

In the drawings: FIGURE 1 is a prespective view of a first embodiment of an ear-insert microphone according to the invention.

FIGURE 2 illustrates the manner in which the apparatus of FIGURE 1 is worn in the ear.

FIGURE 3 illustrates in phantom outline the manner in which the internal parts of the apparatus of FIGURE 1 trating the construction of a third embodiment of the in-.

'vention.

FIGURE 8 is a schematic circuit diagram of the apparatus of FIGURE 7.

FIGURE 9 illustrates the manner in which the apparatus of the invention may be used in conjunction with circumaural protective devices.

FIGURE 10 is a simplified circuit diagram of still an-- other embodiment of the apparatus.

FIGURE 11 is a schematic circuit diagram of a modification of the apparatus of FIGURE 10.

FIGURE 12 illustrates an embodiment of the invention as used in connection with a voice amplifier.

FIGURE 13 is a block diagram of a duplex voice communications system incorporating principles of the invention.

The basic transducer unit of the invention consists of a miniature microphone which is mounted within an ear mold which is custom fitted to be worn in the auricle or pinna of the ear. Sound is conducted from the vocal cords and tformant producing cavities of the mouth and throat to the ear directly through the head of the wearer. Shortcomings of prior ear-insert microphones are overcome by the novel construction described hereinafter. Looking now at FIGURE 1 there is shown a first embodiment of the invention comprising an ear mold '1, which may be fabricated from an acrylic resin or other suitable plastic material. The mold 1 is custom fitted to the ear in a manner Well known to those versed in the art. The mold 1 has -a prong or projection 2 which is adapted to engage the antihelix or inner curved ridge of the outer ear 8 in order to retain the device in place, as shown in FIGURE 2. Conduit 3 extends into the duct leading to the middle ear. Conduit 3 is provided with a hollow passage 4 which communicates microphone 5, mounted within the central portion of the ear mold 1, to the exterior of conduit 3. A pre-amplifier 6 is contained within ear mold 1 and is positioned adjacent microphone as will appear hereinafter.

An interconnecting cord 7 containing a plurality of highly flexible wires serves to connect the pre-amplifier 6 with external utilization circuit-s (not shown). As can be seen in FIGURE 3 the microphone 5 is contained within a surrounding cushion 9 of resilient material such as polyurethane foam. Mold 1 is provided with a central receiving cavity of a dimension suitable to receive cushion 9. Cushion 9 mechanically isolates microphone 5 so that sound and vibration which otherwise might be conducted directly through ear mold '1 will be prevented from reaching the microphone 5. This arrangement will result in the microphone being primarily responsive to sounds transmitted through the air passage 4 of the mold 1. The bottom surface, as viewed in FIGURE 3, of microphone 5 is provided with an aperture 111 which communicates with passage 4. The microphone 5 is preferably terminated in a cavity which presents a proper matching acoustical impedance when the apparatus is placed in the ear. Alternatively, passage 4 and aperture 11 may be dimensioned to provide matching acoustical impedances as will be obvious to those versed in the art.

As mentioned hereinabove, the acoustic spectrum of speech sounds transmitted to the ear directly through the head are deficient in high frequency components. As a result, prior attempts to employ ear-insert microphones have been less than satisfactory due to this increasing attenuation of the high frequencies. There is shown at 12 in FIGURE 4 a curve which is representative of the transmission characteristics of the head. In this graph, frequency is represented along the abscissa and amplitude is represented along the ordinate. Also, there is an overall transmission loss of approximately 20 decibels through the head as compared with air-conducted sound propagated from the lips. In order to overcome both frequency and signal level losses, a pre-amplifier 6 is included within the ear mold 1, having a frequencyversus-amplit'ude transmission characteristic which provides a 9 decibel per octave rise over the sound spectrum of interest. The 9 decibel per octave rising slope includes the microphones response. Curve 13 in FIG- URE 4 represents the transmission characteristics of the microphone 5 and pre-amplifier 6. The resultant response of the system is represented by curve l14. It has been found in a practical construction that the inherent frequency response characteristic of the microphone 5 has a slope of approximately 9 decibels per octave below 2000 cycles per second. Therefore, the pre-amp-lifier 6 need compensate only for the portion of the spectrum above 2000 cycles per second. As can be seen, curve 14 is reasonably flat through the range of interest.

Inasmuch as there exists a significantly lower average sound pressure at the car than at the lips, means must be provided for overcoming this difference in sound level in order to make the present invention functlonally interchangeable with speech microphones used heretofore.

Accordingly, the preamplifier of the present invention also provides an overall gain of approximately 20 decibels at one kilocycle per second and thus will allow its use directly inplace of conventional microphones of the type placed in the region of the lips. The pre-amplifier 6 is preferably contained within the ear-mold 1 itself as shown in FIGURE 3.

An advantage of having the pre-ampli-fier 6 contained within the ear mold housing is that it will minimize unwanted noise pickup in the interconnecting cord 7 which is used to couple the device to related utilization equipment. This is particularly convenient since the ear mold 1 inherently has a volume and a configuration of a size adequate to house the pre-amplifier. That is, an ear mold designed to comfortably conform to the convolutions of the ear 8, in order to seat and retain the device in correct relation to the ear canal, will be found to have a volume ample to enclose the pre-amplifier 6.

Pre-amplifier 6 preferably employs solid-state elements, as will appear hereinafter in connection with the description of FIGURE 6. Cord 7 may contain both the output signal leads as Well as leads for supplying operating potential to the pre-amplifier. If desired, the device may be provided with an energizing battery or cell, thus obviating an external power supply.

Looking now at FIGURE 5, there is shown a modification of the apparatus of FIGURE 1 in which an energizing cell 15 is mounted on the ear mold 1. As can be seen, the surface of the mold 1 is provided with a pair of terminals 16 and 17 in the form of spring contacts adapted to engage opposite faces 18 and 19 of the energizing cell 15. The cell 15 is generally of a tablet shape and may comprise a mercury cell, dry cell, or other similar source of operating potential well known to those versed in the art. Faces 18 and 19 comprise the terminals of the cell 15. The cell may be readily inserted or Withdrawn from terminal clips 16 and .17 without tools or other appliances.

In the embodiment of FIGURE 5, cord 7 is required only to couple the output from pre-amplifier 6 to related equipment. The use of an energizing cell 15 mounted within the device results in its dire-ct interchangeability with conventional microphones in that only two external wire leads or conductors are required and thus obviates power leads going to the microphone as in the case of the embodiment of FIGURE 1.

Looking now at FIGURE 6 there is shown a schematic circuit diagram of a pro-amplifier of a type which may be employed in the apparatus of FIGURES 1-5. Microphone 21 is connected to the base input of transistor 22 via a series resistor 23. Microphone 21 may be of any suitable and well-known construction, such as a subminiature dynamic microphone. The microphone 21 is returned to the positive power supply terminal 24. Operating potential is supplied to the collector of transistor 22 via resistor 27. The output of transistor 22 is coupled to the base of transistor 28 via coupling capacitor 29. The values of the interstage coupling network components are selected to operate as a high pass filter input to the base of transistor 28. The base of transistor 28 is connected to the positive supply 24 via resistor 31 and to the negative supply 25 via resistor 32. The circuit described thus far comprises the input stage 33.

Operating potential is supplied to the collector of transistor 28 via resistor 34 and the emitter of transistor 28 is returned directly to the positive supply terminal 24. The output signal appearing at the collector of transistor 28 is applied to output terminal 35 via coupling capacitor 36. Transistor 28 comprises the output stage 37. As applied to the embodiment of FIGURE 1, the circuit of FIGURE 6 would be energized via terminals 24 and 25 and their corresponding lead wires in cord 7. As applied to the embodiment of FIGURE 5, the energizing cell would be connected between terminals 24 and 25, and cord 7 would carry only lead wires from terminals 24 and 35.

Looking now at FIGURE 7 there is shown an alternative embodiment of the invention having a builtin radio transmitter Which obviates all external wire connections to the device. This embodiment comprises an ear mold 37 generally similar to that shown and described in connection with FIGURE 1. The mold 37 is provided with a conduit 38 which communicates with microphone 39, the output of which is connected to pre-amplifier 41. The mold 37 also houses a radio transmitter 42. The pre-amplifier 41 and transmitter 42 are energized by means of an energizing cell 43. The energizing cell 43 is mounted in an alternate manner to that of FIGURE 5. In this instance the cell 43 is positioned in a plane which is substantially parallel to the exposed surface of the mold 37, rather than normal to the plane of the exposed surface as in the case of the apparatus of FIGURE 5. The outer surface of the cell 43 engages a terminal clip 44 and is retained thereby. A second terminal clip 45 engages the other contact surface of cell 43. Electrical connections between cell 43 and the pre-amplifier are made by means of leads 46 and 47.

Looking now at FIGURE 8, there is shown a schematic circuit diagram of the apparatus of FIGURE 7. The pre-amplifier circuit is enclosed within dotted outline 48 and is identical to the first stage shown at 33 in FIGURE 6. The output of stage 48 comprises an audio signal which is supplied to the base of transistor 49 via coil 51. Stage 48 operates as a modulator in the circuit of FIG- URE 8. Capacitor 52 is connected between the positive terminal of cell 43 and coil 51. The collector circuit of transistor 49 includes a tank circuit comprising coil 53 and capacitor 54. Coil .53 is inductively coupled to coil 51 and thereby comprises an oscillator circuit which will generate a radio frequency carrier. Capacitor 55 is connected in shunt relationship with the energizing cell 43. The audio signal applied to coil 51 will modulate the carrier which is radiated directly from coil 53. The radiated carrier may be picked up by any suitable radio receiver as will be obvious to those versed in the art. As can be seen, this embodiment is entirely self-contained and self-powered and may be worn inconspiciously and without interfering with the helmet or other appurtenance of an astronaut or the like. Since it is intended that the receiver, which is responsive to the device of FIGURE 8, be located in relatively close proximity to the wearer, no transmitting antenna is required. The tank circuit coil 53 is relied upon for radiation of the modulated carrier. The RF oscillator portion of the circuit is shown within dotted outline 50.

Looking now at FIGURE 9, there is shown the manner in which the apparatus of FIGURES 1, or 7 may be used in conjunction with circumaural protection devices of the type commonly referred to as car defenders. These comprise earmuif type devices which greatly attenuate ambient sounds. This arrangement is particularly adaptable to the embodiment of the invention shown in FIGURE 7 since it is unnecessary to employ interconnecting wires, cords or leads to the ear which would necessarily pass between the exterior surface of the head of the wearer and the confronting surface of the ear defender 57.

The ear microphone element identified as 5 in the apparatus of FIGURES 1-3 and as element 39 in FIGURE 7 may comprise an electroacoustical transducer which is also suitable for the generation of sound in response to an electrical input signal. By employing such an element in a transceiver circuit, of the type to be described hereinafter, two-way communication may be obtained. That is, such an electroacoustical transducer used in conjunction with a duplex circuit of the type shown in FIGURE will permit two-way radio communication between the wearer and a remote transceiver station. The duplex circuit of FIGURE 10 comprises electroacoustical transducer 61, a radio transmitter 62, a receiving coil 63 responsive to the signal transmitted from the remote transceiver station and an impedance balancing network 64. The exact circuit parameters of the impedance balancing network 64 depend on the characteristics of the electroacoustic transducer used. Generally, it consists of series and/ or parallel combinations of L, C and R. The circuit also includes a network comprising resistors 65 and 66. In the duplexing system shown in FIGURE 10 the receiving coil is responsive to a radiated magnetic field and the transmitter radiates a modulated RF signal. The impedance balancing network isolates the transmitter 62 output from the receiving coil 63.

Looking now at FIGURE 11, there is shown an alternative duplexing system in which the received signal is in the form of a modulated radio carrier rather than a magnetic induction signal as in the case of the apparatus of FIGURE 10. As in the previously described duplexing system, the apparatus is self-contained and self-powered.

The transducer 67 comprises an electroacoustical transducer element, preferably of the dynamic type, which is designed to reproduce speech as well as operate efficiently as a microphone.

The receiver portion of the duplexer circuit comprises a receiving coil 68 and a shunt capacitor 69 which comprise a resonant tank circuit which may be tuned to the frequency of a radio transmitter (not shown) used to communicate with the wearer of the duplexer. Capacitor 69 is made variable for this purpose. The incoming radio signal is demodulated by a diode detector 71. The receiver output is connected to transducer 67 via an impedance balancing network 72. Resistor 73 and capacitors 74 and 75 comprise impedance balancing network 72. The transmitter portion of the duplexer circuit comprises a preamplifier stage 76 which is substantially the same as that shown at 48 in FIGURE 8.

Transducer 67 is shunted by resistor 77. The receiver circuit 70 and the pre-amplifier circuit 76 are interconnected by means of the network comprising resistors 78-79 and coupling capacitor 81. The output of the preamplifier 76 is used to drive the transmitter 82 which is substantially the same as that shown at 50 in FIGURE 8. The impedance balancing network 72 will prevent the output of transmitter 82 from overloading the input of the receiver circuit. In a practical embodiment, the transmitting and the receiving channels are assigned different frequencies to further minimize undesirable interaction of the input and output signals of the apparatus of FIGURE 11.

Looking now at FIGURE 12, there is shown still another embodiment of the invention as applied to a voice amplification system. This embodiment is particularly useful in connection with speech transmission in conjunction with respiratory protective devices. Respiratory devices as herein intended include both air supply respira tors and devices usually called gas masks as well as selfcontained breathing apparatus. It has been found that speech characteristics of respirators are generally so poor that personnel wearing them in a toxic atmosphere are frequently forced to remove the mask from their faces in order to talk. In addition to severe frequency discrimi nation through various portions of the speech spectrum, there is a severe insertion loss introduced by various respiratory protective devices. These characteristics preclude efliective speech communication of any kind in a noisy environment. The present invention provides a means for readily overcoming the problems associated with speech communication via respiratory devices of the prior art.

Looking now at FIGURE 12, there is shown an individual 83 wearing a dust respirator 84 or protective respiratory device. An ear-insert microphone 85 of the type shown in FIGURE 1 is connected to amplifier means 86 worn externally by the individual 83. The amplifier means comprises an audio amplifier and a loudspeaker 87 together with the necessary self-contained power supply for operation. The amplifier means 86 may be supported from a strap or band 88 worn around the neck. Speech picked up by microphone 85 is sent via cable 89 to the amplifier means 86 Where it is amplified and projected from loudspeaker 87 at a level equal to, or higher than that of the voice of individual 83 when not wearing the protective respirator device 84. As can be seen, microphone 85 does not interfere in any way with the respirator 84. Furthermore, any existing type of respiratory device may be used since the microphone 85 is not located in the facial region.

Looking now at FIGURE 13, there is shown still another embodiment of the invention, which is particularly useful in an aero-space environment or other environment which may have an excessive ambient noise level. The system shown in FIGURE 13 comprises a two-way speech communications system which increases the intelligibility of transmitted speech under conditions of high ambient noise at the listening location, the transmitting location, or in the transmission link itself. This system makes use of the fact that the human ears are responsive to the direction of arriving sound and rely on both amplitude and arrival time differences for information. That is, the brain can detect phase differences in the sound received at the two ears in order to provide a directional sense as to the point of origin of the sound. If two or more sounds are being generated at different locations in space, the listener has the ability to mentally discriminate against one or the other of the locations so as to concentrate upon one sound to the exclusion of the other sound. Such a system operates by taking a speech signal existing in a single channel and transmitting it through a phase shifter capable of applying a constant phase shift to all frequencies in the speech spectrum. A second channel carries the unaltered speech signal; therefore a precise but different time delay exists in one channel as compared with the other for every individual frequency component in the speech sound spectrum. In a practical system the phase shift applied to the one channel may be 90.

A 90 phase shift represents 2.5 milliseconds difference at 100 cycles, 250 microseconds at 1,000 cycles per second, and 25 microseconds at 10,000 cycles per second. If these three frequencies are transmitted to separate earphones located in respective ones of the two ears of the listener, and the 90 phase relationship maintained, the apparent location in space of the three frequencies will be different.

Individual voices have characteristic transients which contain a band of identifying frequencies. These become locating frequencies in a system of this type. If several voices, hum, and static are all being transmitted over a single transmission link, a system of this type will cause the hum to appear to emanate from one point, the voice from another point and so on. The listener will subjectively locate the desired sound in space and mentally discriminate against the others. This discriminatory operation would be impossible if all sounds were emanating from the same transducer.

A typical modification of the present invention incorporating the above-described system is shown in FIG- URE 13. Speech from a sound source of interest is picked up by any suitable microphone 91 and amplified via amplifier 92. The output of amplifier 92 is supplied directly to radio transmitter A (identified as 93) and is supplied to radio transmitter B (identified as 94) via a 90 phase shifting network 95. The unaltered signal is radiated from antenna 96 and received by a suitable radio receiver 97 capable of reproducing the original signal picked up by microphone 91. The audio output of receiver 97 is heard by the right ear of individual 98. That is, receiver 97 is responsive to transmitter A (93) and is heard by the right ear. Individual 98 has a duplexer 99 8 worn in the left ear which is of the type shown and described in connection with FIGURE 11.

The signal from transmitter B (94) is radiated by antenna 101 and is picked up by the receiving circuit of duplexer 99. By reason of the delay introduced in the channel transmitted by transmitter B, the individual 98 may subjectively discriminate against undesired sounds. Thesystem can, of course, be implemented to provide a similar function in the reverse direction of transmission. Specifically, the transmitting portion of duplexer 99 will transmit speech picked up through the head of individual 93 to receiving antenna 102.

The unaltered speech signal from duplexer 99 is received by the receiver 103 and reproduced directly via loudspeaker 104. The speech signal from receiver 103 is also supplied to a phase shifter (105). Phase shifter 105 is similar to phase shifter in that it applies a constant or fixed delay to all frequencies throughout its pass band. The phase shifted output from phase shifter is reproduced via loudspeaker 106.

Inasmuch as each of the functional units represented by a rectangle in FIGURE 13 may be any one of the numerous devices for each respective function well known in the art it is deemed unnecessary to show circuit details. A suitable phase shifter is shown and described in a paper entitled A Simple Wideband 90 Phase Splitter for Speech or Music by Lawrence V. Kriger, published by the Air Force Cambridge Research Laboratories (Cataloged by ASTIA as AD No. 271757).

The loudspeakers 104 and 106 are displaced in space, preferably by a distance of approximately 7 feet, in order to spatially distribute the apparent source of the several frequencies comprising the speech spectrum. This will permit a listener, physically located between and in front of loudspeakers 104 and 106, to subjectively discriminate against unwanted sounds.

Thus, there has been shown and described hereinabove novel and improved apparatus for the transmission of speech, such exposition being sufiicient to enable those skilled in the art to practice it.

Since certain changes may be made in the techniques, devices and systems without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Apparatus for transforming speech into electrical signals comprising:

a unitary plastic ear mold adapted to conform to the outer ear and thereby block the transmission of ambient sound to the middle ear, and having projection means for retaining said mold in the auricle of said outer car;

an enclosure of resilient material located within said ear mold;

microphone means located within and substantially surrounded by said resilient enclosure;

a conduit defining a sound passage for acoustically coupling said microphone means with the duct leading to said middle ear, Via an aperture in said enclosure whereby said apparatus is responsive only to the voice of the wearer; and

conductor means extending from said microphone means whereby said microphone means may be connected to a utilization circuit.

2. Apparatus as defined in claim 1 having a preamplifier mounted within said ear mold, the input of said pre-amplifier being connected to said conductor means and having lead means extending therefrom whereby said pro-amplifier may be connected to said utilization circuit, said pre-amplifier having an amplitude versus frequency response characterized by an increase in gain of substantially 9 decibels per octave from approximately 1,000 cycles per second to approximately 10,000 cycles per second.

3. Apparatus as defined in claim 2 having an energizing cell supported by said ear mold and connected to said pre-amplifier for supplying operating potential thereto. 4. Apparatus as defined in claim 3 including circumaural protection means enclosing said outer ear whereby ambient sounds are substantially prevented from reaching said microphone means.

5. Communication apparatus adapted to be worn in the ear comprising:

a unitary ear mold adapted to be worn in the outer ear and retained therein by engagement with the auricle thereof;

an electroacoustical transducer ear mold;

a conduit connecting said transducer with the exterior of said ear mold;

radio receiver means mounted within said ear mold and connected :to said transducer whereby received radio signals may be converted to audible signals for propagation through said conduit;

transmitter means mounted within said ear mold and connected to said transducer whereby sounds received via said conduit may be transmitted as radio signals; and

duplexer means connected to said transducer whereby the output from said transmitter is effectively isolated from the input of said receiver.

6. Speech communication apparatus comprising:

a first ear mold adapted to be worn in one ear of a human being, said ear mold containing a selfpowered radio receiver; and

an electroacoustical reproducer;

a second ear mold adapted to be worn in the other car of said human being, said second ear mold containing transceiver duplexer means; and

an electroacoustical transducer connected thereto whereby speech sounds from said human being may be picked up by said transducer and transmitted on a radio carrier and received radio signals may be transformed into sounds audible to said human being;

a remote audio signal source;

a first transmitter connected to said source and adapted to transmit signals to said receiver;

phase shifting means connected to said source for uniformly shifting the phase of signals from said source by 90;

a second transmitter connected to said phase shifter for transmitting signals to the receiver portion of said transceiver means whereby the audible signals heard by said other ear from said audio source are shifted by 90 with respect to the audible sounds heard by said one ear from said source.

7. Apparatus for transforming speech into electrical signals comprising:

a unitary plastic ear mold adapted to conform to the outer ear and having a projection means for retaining said mold in the auricle of said outer ear;

an enclosure of resilient material located within said ear mold;

microphone means located within and substantially surrounded by said resilient enclosure;

a conduit communicating the exterior of said mold with said microphone means via an aperture in said enclosure;

conductor means extending from said microphone means whereby said microphone means may be connected to a utilization circuit;

a pre-amplifier mounted within said ear mold, the input of said pre-amplifier being connected to said conductor means and having lead means extending therefrom whereby said pre-amplifier may be connected to said utilization circuit, said pre-amplifier having an amplitude versus frequency response charmounted within said acterized by an increase in gain of substantially 9 decibels per octave from approximately 1,000 cycles per second to approximately 10,000 cycles per second;

an energizing cell supported by said ear mold and connected to said pre-amplifier for supplying operating potential thereto; and

a radio transmitter mounted within said ear mold and connected to said energizing cell and to said preamplifier whereby speech signals picked up by said microphone means are transmitted on a radio carrier.

8. Speech amplification apparatus adapted to be worn on the person, comprising:

an ear mold for acoustically isolating the outer ear from the middle ear, said ear mold having a central cavity therein and a sound transmitting passage extending therefrom into the duct leading to the middle car;

a microphone resiliently mounted within said cavity and acoustically coupled to said conduit whereby said microphone is responsive only to the voice of the wearer as transmitted via said duct;

a self-powered audio amplifier having the input thereof connected to said microphone; and

loudspeaker means adapted to be carried on the person of said wearer and connected to the output of said amplifier whereby the voice of said wearer picked up by said microphone is audibly reproduced from said loudspeaker means.

9. An ear insert microphone adapted to be worn in the ear, comprising:

an ear mold conforming to the convolutions of the outer ear in order to substantially prevent ambient sound from entering the duct leading to the middle ear, said mold having a hollow central receiving cavity therein;

a projection extending from said ear mold for retaining said mold in the auricle of the outer ear;

a conduit extending from said ear mold and defining a sound passage between said cavity and said duct; and

microphone means contained within said cavity in acoustic coupling with said passage whereby said microphone means is responsive only to sound received via said duct and wherein the sound passage in said conduit is dimensioned to present a matching acoustical impedance between said duct and said microphone means when said ear mold is worn in the ear.

10. An ear insert microphone as defined in claim 9 wherein the sound passage in said conduit is dimensioned to present a matching acoustical impedance between said duct and said microphone means when said ear mold is worn in the car.

11. An ear insert microphone as defined in claim 9 including:

a cushion of resilient material substantially surrounding said microphone means to mechanically isolate said microphone means from sound transmitted through the solid portion of said ear mold.

References Cited by the Examiner UNITED STATES PATENTS 2,535,063 12/ 1950 Halstead 179--1 X 2,544,102 3/1951 Pease 179-1 2,946,862 7 A1960 Wadsworth et a1 "179-156 2,950,357 8/1960 Mitchell et al 179-1 2,971,065 2/ 1961 Busse 179107 3,042,749 7/ 1962 Johnson 179-1 3,087,028 4/1963 Bonnin 179-156 KATHLEEN H. CLAFFY, Primary Examiner. WILLIAM C. COOPER, ROBERT H. ROSE, Examiners. A. J. SANTORELLI, R. MURRAY, Assistant Examiners. 

1. APPARATUS FOR TRANSFORMING SPEED INTO ELECTRICAL SIGNALS COMPRISING: A UNITARY PLASTIC EAR MOLD ADAPTED TO CONFORM TO THE OUTER EAR AND THEREBY BLOCK THE TRANSMISSION OF AMBIENT SOUND TO THE MIDDLE EAR, AND HAVING PORJECTION MEANS FOR RETAINING SAID MOLD IN THE AURICLE OF SAID OUTER EAR; AN ENCLOSURE OF RESILIENT MATERIAL LOCATED WITHIN SAID EAR MOLD; MICROPHONE MEANS LOCATED WITHIN AND SUBSTANTIALLY SURROUNDED BY SAID RESILIENT ENCLOSURE; A CONDUIT DEFINING A SOUND PASSAGE FOR ACOUSTICALLY COUPLING SAID MICROPHONE MEANS WITH THE DUCT LEADING TO SAID MIDDLE EAR, VIA AN APERTURE IN SAID ENCLOSURE WHEREBY SAID APPARATUS IS RESPONSIVE ONLY TO THE VOICE OF THE WEARER; AND CONDUCTOR MEANS EXTENDING FROM SAID MICROPHONE MEANS WHEREBY SAID MICROPHONE MEANS MAY BE CONNECTED TO A UTILIZATION CIRCUIT. 